This invention relates generally to the field of specialized furniture suitable for use by invalids and relatively infirm persons, and more particularly to an improved form of chair having means for assisting an occupant to gain a sitting as well as a standing position. Devices of this general type are well known in the art, and the invention lies in specific constructional details which permit ease of manufacture at relatively low cost, and improved facility in use by the occupant.
The most commonly used type of such chair in the prior art is one in which the seat bottom is hingedly associated with the chair frame adjacent a forward edge thereof. A hydraulic or pneumatic lifting means is either electrically or manually powered, and when actuated, the occupant is raised with the seat to a standing position as the seat bottom moves from horizontal to vertical orientation. Such constructions are not without substantial utility, particularly in the area of use by relatively feeble and/or grossly overweight persons. However, they are expensive to construct, and, depending upon the quality of manufacture, they are more or less reliable. They suffer a substantial disadvantage in that upon the occurrence of a power failure, electrically powered types become at least temporarily inoperative. Hand powered hydraulic types, somewhat similar to a barber's chair, often require manual exertion for operating far above the ability of the user, and are thus suitable only for use with an attendant.
The above described constructions have been used primarily in homes, or patient's rooms in nursing hospitals on a personal basis where the occupant often spends the better part of the day. The high cost of manufacture normally prohibits the provision of large numbers of such chairs and the placing ofthe same about the private or nursing home.
Many occupants of nursing homes, as well as those living in private homes, do possess a degree of ambulatory ability, but find that it requires more than normal effort to sit or arise from a conventional chair. These persons, once erect, can walk with some assistance from one location to another where they will again sit down in another chair at another location. Such persons do not require powered chairs at each location and, indeed, the cost of such chairs in plural numbers is usually prohibitive.
The use of unpowered chairs which rely upon compressed springs to elevate a seated individual to standing position are not unknown. An interesting construction is disclosed in the U.S. patent to E. J. Hoff, U.S. Pat. No. 1,025,915, granted May 7, 1912. The disclosed structure includes a seat supported on an articulated linkage having a principal pivot point located several inches rearwardly at the front edge of the seat. The linkage extends beyond the pivot point, and is engaged by a pair of very powerful springs, the tension of which is adjustable. The springs are always under substantial tension, which is increased as the seat is lowered under the weight of the occupant, and means is provided for locking the seat in lowered position such that the locking means cannot be released unless the occupant is sitting on the seat, thereby avoiding accidental movement of the seat from lowered to raised position, with possible injury to a bystander. The complexity of the construction, coupled with the fact that the force exerted by the springs under tension, is many times that of the weight of the occupant, forces the construction of the chair to be unreasonably heavy as well as expensive, and, as a result, this type of chair construction has not gained public acceptance.